Warehouse distribution centers receive large numbers of goods from the manufacturers which must be efficiently sorted, packed and shipped in accordance with orders from customer stores. Typically, the goods arrive and are sorted into "stock keeping unit" or "SKU" batches by type, size, color, etc. These SKU batches are then transferred to a "pick face" where workers select from among the batches as they arrive and distribute them among one or more shipping cartons or containers according to written manifests. Delivery to the pick face is typically via conveyor-type racks which transport the batches in order of loading to workers stationed at their opposite ends, the "pick face". Conveyor or other take-away means are usually provided at the pick face, receiving filled shipping cartons and transporting them to other parts of the distribution center for further processing and loading onto waiting transport vehicles.
The SKU batches are typically identified by an SKU number, which is a barcode-type identifier for a particular type, size, color of goods. All of the items or sets of items in an SKU batch are typically the same merchandise and have the same SKU number.
There may be dozens or hundreds of flow racks in a pick face, with workers typically servicing more than one rack at a time. Hundreds or thousands of containers/cartons may move along the pick face throughout the day. Because the skill level and efficiency of the workers vary, and because some batches are more difficult to pick and "put" in the cartons, it is desirable to assign the workers along the pick face in a manner to optimize their efficiency throughout the day.
Another factor to consider is the sequence in which orders from customer stores need to be filled throughout the day. This is very often determined by, or decides, the order in which the trucks for particular stores are parked in a loading area for receiving filled containers. It is therefore also desirable to optimize the sequence in which the containers or cartons are moved along the length of the pick face. For example, the first store whose order must be satisfied may require goods from SKU batches on flow racks which are widely spaced along the pick face, and as that store's carton moves along the pick face it will skip over a substantial portion of the pick face between relevant SKU batches.
Prior art picking systems in which workers operate using written manifest or picking lists are less than ideal for modern distribution centers. This is due primarily to their inability to update or adjust picking assignments to reflect changing conditions, and their over-reliance on the memory of the worker running between flow racks and cartons with written list in hand. These prior art systems also have no real-time flexibility to allow for the correction of mismatches between SKU batch quantities and cartons.
More recently, a number of paperless, partially computerized order picking systems have been proposed to overcome the disadvantages of paper-based picking systems. Examples include U.S. Pat. No. 4,792,273 to Specht; U.S. Pat. No. 4,921,087 to Nakamura; JA 0147603; JA 0221004; JA 0162605; JA 0007605; JA 0267604.
JA 0007605 shows a movable picking truck on which the worker rides, the truck running along fixed shelves where goods are to be picked. The truck is driven by a tape-recorded program, and includes a display indicating the good or goods to be picked from the shelf.
JA 0267604 discloses a picking carrier on which the worker rides, the carrier moved around a circuit of fixed shelves. The carrier includes a computer controller 24 and is operated by a managing computer with radio transmission instructions. The controller is provided with indicators to aid the worker in making selections from the shelves or racks. The picked goods are stored on the carrier itself.
JA 0162605 discloses a number of quantity indicators arranged at fixed positions along a pick face, with a central conveyor belt to carry cartons along the pick face. Each quantity indicator is provided with a total quantity indicator and a completion key. The quantity indicator shows the number of goods to be picked from racks in a fixed picking zone, and the completion of picks from each rack is entered with the completion key. When all of the indicated picks have been made in the picking zone, the completion of picks is confirmed with the indicator.
JA 0221004 discloses a number of fixed racks or shelves spaced along a central conveyor, each shelf provided with a lamp indicator, a quantity display and a control unit. A second quantity display is provided on a movable gantry frame which can be moved along the line of shelves. The lamp indicator is lit when goods need to be picked from a particular shelf, the gantry is moved to that shelving unit, the quantity display on the gantry is connected to the central control unit on the shelf, and the number of goods to be picked is indicated on the gantry-mounted display.
JA 0147603 discloses a number of fixed, fluidized shelving units each provided with a fixed goods pickup verification indicator and a lamp indicator operated by a centralized control system.
While the above prior art paperless pick systems are an improvement over the older paper-based systems, they still do not provide the system flexibility and update capabilities needed to truly optimize picking operations. Moreover, their lack of flexibility requires structural redundancy in large applications, making them unsuitable for large scale use without greatly increasing the cost of such systems. These prior art systems are also extremely limited in terms of operator interface and input in the picking process to adapt to unforeseen conditions.
These and other drawbacks of the prior art are eliminated in the picking system of the present invention.